8/5- Arrhythmias Flashcards
What is a normal QRS complex time/width? Long?
Normal is ~120 ms, long is anything over about 140
What are the 3 steps in diagnosing any arrhythmia?
- Determine if the QRS complexes are narrow or wide
- Determine if the QRS complexes or regular or irregular (distance of more than 1/2 a box between complexes)
- Determine if P waves or evidence of atrial activity are present (relation between P wave and QRS)
What are possible arrhythmias if QRS complexes are narrow and regular?
- Sinus tachycardia
- Atrial tachycardia
- Atrial flutter
- AVNRT
- AVRT
What are possible arrhythmias if QRS complexes are narrow and irregular?
- MAT
- Atrial flutter with variable conduction
- Atrial fibrillation
What are possible arrythmias if QRS complexes are wide?
- SVT with BBB
- Ventricular tachycardia
What is this? Analyze
- HR ~ 150 bpm (tachycardia)
- Positive upright (normal) P waves in front of every QRS complex (1:1 P:QRS ratio)
- QRS is nice and slim; no conduction problem down from the atrium
- Limited analysis because there’s only 1 lead, but this P wave morphology may indicated sinus wave tachycardia
Most likely: sinus tachycardia
- This is just a rate problem
What is sinus tachycardia typically a response to?
Sinus tachycardia is almost always a physiologic response
What may cause sinus tachycardia?
- Hypotension
- Hypovolemia/anemia/acute bleed
- MI/depressed EF/tamponade
- Hypoxemia
- Fever
- Anxiety/pain
- Medications
- (Hyperthyroidism)
What other types of sinus tachycardia are present (rarely)?
- Sinus node reentrant tachycardia
- Non paroxysmal sinus tachycardia
- Postural orthostatic tachycardia syndrome (POTS)
What is this?
- P wave present before every QRS complex (this is probably ~ lead II: P waves are negative)
- P wave looks a little uncharacteristic (although only 1 lead here): ectopic P waves (anything originating from any other place than the sinus node)
Ectopic atrial tachycardia
What are some common causes of atrial tachycardia?
- Structural (atrial) heart disease/diseased atria
- Sympathetic stimulation
- Toxins/drugs
What is the heart rate range for atrial tachycardia?
120-250 bpm (typically ~ 160)
T/F: Atrial tachycardia typically causes hemodynamic compromise?
False; atrial tachycardia usually does NOT cause hemodynamic compromise
Treatments for atrial tachycardia?
- Withdraw sympathetic stimuli/drugs
- Rarely (if ever) use antiarrhythmics
- Often does not respond to cardioversion
What is this? Analyze
Atrial Tachycardia with Block (PAT with Block)
- Arrows pointing at P waves (negative here)
- No 1:1 conduction here; P waves too fast and ventricles can’t respond to each one. You basically see conduction every 4th P wave
- “Block” from inability of AV node to handle atrial tachycardia rate; may be protective, but bad if it causes heart rate to drop too low
What could cause atrial tachycardia with block (PAT with block)?
Digoxin toxicity
What is a common treatment for really any type of tachycardia?
Catheter ablation
What is this? Analyze
- Continuous undulation of isoelectric line; no straightish segment between P waves
- Sawtooth line pattern of isoelectric line
Atrial flutter
What does the conduction pattern look like in atrial flutter?
Depolarization is traveling continuously in an atrial circuit; there’s basically no free atrial activation that would create straight isoelectric line between P waves
What may cause atrial flutter?
Diseased or dilated atria
What is the heart rate in atrial flutter?
Usually 300 (with 2:1 AV block)
Treatment for atrial flutter?
- Unstable: synchronized cardioversion (shock the pt)
- Slow AV conduction (Metoprolol, Verapamil or diltiazem, not digoxin acutely)
- Convert back to sinus
- Recently, anticoagulate like AF (stagnant blood in parts of the atria may cause clots… -> brain)
What is this? Analyze
- Narrow complex tachycardia; regular
- Don’t see clear P wave
Narrow complex QRS tachycardia with no regular P wave; there are 2 possibilities from here:
- AVNRT or AVRT??
What is AVNRT (name)? What is the conduction pathway?
AV Nodal Re-Entrant Tachycardia (AVNRT)
- Rhythm originates in AV node
- Atria and ventricles are activated almost simultaneously, thus P and QRS occur almost the same time (P waves can’t be observed)
What causes AVNRT?
“Micro-reentrant pathway”
- Usually “paroxysmal”, often triggered by PAC
- Rarely correlated with any heart disease; occurs in structurally normal hearts (?)
Treatment for AVNRT?
- Unstable: cardiovert
- Block AV conduction:
—Vagal-enhancing maneuvers
—Adenosine (6 mg,12,12): almost always works
—Verapamil or Diltiazem
—Beta blockers
- Ablation
What is this? Analyze
- Cousin to AVNRT, but this AVRT
- There is a P wave (outside the QRS; commonly not seen)
What is AVRT? What is the conduction pathway?
AV Re-entrant Tachycardia (AVRT)
- Both atria and ventricle are equal participants in tachycardia
- Conduction happens in reverse from ventricle to atrium; don’c contract simultaneously (ventricles first)
- May see retrograde P wave distorting ST segment
- This is orthodromic (anti-dromic could have reversed conduction path and weird ventricle pattern)
What causes AVRT?
“macro reentrant loop” involving bypass tract
- Usually “paroxysmal”
Orthodromic conduction (shown earlier) occurs in ___% of cases while antidromic (may resemble VT) occurs in ___%
Orthodromic: 90-95%
Antidromic: 5%
Treatment for AVRT?
- Unstable: cardiovert
- Stable: block or slow AV node conduction
- Ultimately: ablation
The following distinguishing characteristics of narrow complex regular tachycardia point to what types of arrhythmias?
- Normal P waves ->
- Abnormal P waves ->
- Flutter waves ->
- No atrial activity ->
- Normal P waves -> sinus tachycardia
- Abnormal P waves -> atrial tachycardia
- Flutter waves -> atrial flutter
- No atrial activity -> AVNRT or AVRT
What is this?
Multifocal Atrial Tachycardia (MAT)
Conduction pattern in MAT?
How can MAT be diagnosed?
- 3 or more distinct P waves
- Ventricular rate 100
What cuases MAT?
Usually occurs in pts with pulmonary disease, esp COPD
Treatment for MAT?
- TREAT UNDERLYING DISEASE
- Try to decrease sympathomimetics
- Attempts to suppress arrhythmia or block AV conduction are usually futile*
What is this?
Atrial flutter (with variable conduction)
What is the conduction pattern in atrial flutter?
What is this?
Atrial fibrillation
What is the conduction pattern in atrial fibrillation?
- May also be due to focus in pulmonary vein
What may cause atrial fibrillation?
- HTN
- Ischemia/CAD
- Atrial dilation (MV disease, etc)
- Toxins
- Pericarditis
- Pulmonary emoblus
- Hyperthyroidism
- Vagal or sympathetic mediated
- (Pulmonary vein)
Many AF causes may be caused by focus in pulmonary vein
Nomenclature in atrial fibrillation:
- Paroxysmal, episodic:
- Persistent:
- Permanent:
Nomenclature in atrial fibrillation:
- Paroxysmal, episodic: AF converts to NSR spontaneously
- Persistent: AF terminates only after intervention
- Permanent: AF resists attempts to restore NST
Treatment for atrial fibrillation?
- Unstable: cardiovert
- Stable: slow ventricular response rate or electively cardiovert
- If in afib > 48 hrs or unknown time, anticoagulate or obtain TEE to r/o thrombus; then cardioversion and/or ibutilide
Recap: The following distinguishing characteristics of narrow irregular tachycardia point to what types of arrhythmias?
- Multiple different P waves ->
- Flutter waves ->
- No atrial activity ->
Narrow irregular tachycardias:
- Multiple different P waves -> MAT
- Flutter waves -> atrial flutter
- No atrial activity -> atrial fibrillation
What is this? Analyze
“Boringly regular” QRS complexes in WCTs due to SVT
What is this? Analyze
Slightly irregular QRS complexes in VT
What is the conduction pattern in atrial and ventricular dissociation in ventricular tachycardia?
(P wave dissociation/AV dissociation)
What is this? Analyze
VT with AV dissociation
What is the conduction pattern in ventricular tachycardia?
What may cause ventricular tachycardia?
- Acute ischemia or acute myocardial infarction
- Reentry around old scar or aneurysm
- Medications that prolong QT interval
Treatment for ventricular tachycardia?
- Unresponsive or pulseless: defibrillation
- Unstable: synchronized cardioversion
- Stable: antiarrhtyhmic agents
What is this?
Ventricular tachycardia: Torsades de Pointes
What is this?
Atrial tachycardia with block; flutter
What is this?
Multifocal atrial tachycardia
- see 3 or more morphologies
What is this?
Sinus tachycardia with bundle branch block
- Rate here is little more than 100
- Note aVL and V1 leads
What is this?
?
What is this?
?
What is this?
?
What is this?
?
Side effects of antiarrhythmic therapy?
- Negative inotropy
- QT prolongation and torsades de pointes
- Pro-arrhythmic
* Suppressing PVCs increases death
* Treating atrial fibrillation by trying to suppress the arrhythmia is not better than anticoagulating and controlling the rate
* AICDs (defibrillators) are better than antiarrhyhmics in pts with ventricular tachycardia (VT)
What is Amiodarone?
Drug for antiarrhythmic therapy
- Beta blocking, Ca-channel blocking, and direct; acts on SA node, AV node, atrial and ventricular tissues
- When starting: follow for bradycardia and heart block
- Longer term (q6 mo): liver function tests, thyroid function tests (esp TSH), CXR (pulmonary fibrosis)
- Important drug interactions: increases INR, increases digoxin level
- Useful loading dose: bolus, then 1 mg/kg/hr; 400 BID-TID
- Usual maintenance dosing:
—Atrial arrhythmias; 100-200 qD
—Ventricular arrhythmias: 200-400 qD
